[Therion] compass correction Re: Strange Therion/survex disparity

[Alastair Gott]

Hi therion people,

I’m working on the dataset again with my friend.

We’ve found that the survex model uses a compass calibration in some places and are trying to work out if this needs transposing across to the therion model.
 But in the process I have found out that when we give therion a compass reading it’s always taking off 0.9 to 1 degree from the reading given in the .th data.

I’ve just run changes to entrance-boulder in both therion and survex. Below results just for first leg 1-2

No date+compass calib= 133.6 deg survex// 132.6 deg therion
Date + no compass calib=131.0 deg survex// 130.1 deg therion
No date+no compass calib=131 deg survex// 130deg therion
Date + compass calib=133.6 deg survex// 132.7 deg therion

So clearly therion is correcting the data 1[] 2[] 13.4[] 131[] 10.0
By always taking one degree off the compass irrespective of what we tell it.

(For information: When calibration used survex= *calibrate compass -2.65 // therion= calibrate compass 357.35)

Does anyone have any ideas where therion is pulling this 1 degree correction from?


Regards,
Alastair Gott.

> On 26 Feb 2021, at 07:43, A Gott <alastairgott at gmail.com> wrote:
> 
> HI Tarquin and Andrew,
> 
> Many thanks for that, We were just lost, I think we'll be able to pick it up from here with your helpful guidance. Should just be a case of looking through the .th files and looking for all the 90's
> 
> I hope you are both well.
> 
> Al.
> 
>> On Fri, 26 Feb 2021 at 07:33, Andrew Atkinson <andrew at wotcc.org.uk> wrote:
>> 
>> > DOWN has been mis-converted into +90 rather than -90, when converting
>> > from Survex format to Therion format.
>> > Survex:
>> > 2213  2212    B       3.49    -       DOWN
>> > Therion:
>> > 2213  2212    3.49  311  90
>> > I'm guessing that error may turn up elsewhere. consort_climax looks
>> > similarly wrong.
>> As a point to note -90 and Down at treated differently for clino 
>> correction, they can be treated ed the same
>> 
>>  From the survex manual
>> 
>>      "*infer plumbs on" tells cavern to interpret gradients of +/- 90 
>> degrees as UP/DOWN (so it will not apply the clino correction to them). 
>> This is useful when the data has not been converted to have UP and DOWN
>> 
>> Andrew
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